blown lower intake manifold gasket? | Ford Explorer Forums - Serious Explorations

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blown lower intake manifold gasket?

YBCold

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Hey guys so heres some background got the car over the summer with the cooling system full of water and rust ,power flushed till clean then installed a fail safe thermostat that seems to have failed shut.

Couple of days ago i noticed an external leak by the housing upon closer inspection its coming from behind and underneath the housing right where IIRC the Lower intake mates with engine. So bad infact i could hear it hissing when i was draining the coolant. Got ghe upper off today and found coolant and some oil near the rear of the upper closest to the fire wall is this a bad head or lower intake gasket? I almost got the valve covers off today and the lower.
 



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I could be wrong, but I would bet it is the LIM.

When you install the LIM gasket, part of the procedure is to apply RTV sealant to the junction of the LIM gasket and the valve cover - the far back corners where the LIM meets the valve cover surface. Its a common place for leaks to occur.

Further, to correctly torque the LIM to specs and ensure no leaks, you need to tighten the LIM bolts as you apply torque to the head bolts. In other words, the heads and the LIM bolts are to be torqued together as a set. This means loosening the head bolts and then re-torqueing them with the LIM bolts.

But, they, the head bolts are not reusable.

Having said that, I have successfully replaced LIM gaskets without redoing the head bolts, but it isn't typically successful. YRMV
 






quick question i dont remember how to alternate between head bolts and LIM bolts. haynes manual says they have to alternate but not sure if LIM then L and R or if its L LIM R
 






I just double checked, and there is nowhere I can find that says you have to torque the head at the same time as the intake manifold. When I did mine, I did it to the Haynes manual, which showed a basic alternating pattern of just the lower intake manifold. I've done it on two 4.0's now, and neither has failed. RTV in the valley is to keep oil in, not coolant.
 






I just double checked, and there is nowhere I can find that says you have to torque the head at the same time as the intake manifold. When I did mine, I did it to the Haynes manual, which showed a basic alternating pattern of just the lower intake manifold. I've done it on two 4.0's now, and neither has failed. RTV in the valley is to keep oil in, not coolant.

x2 on this. I did mine and only worked on the LIM, never touched the head bolts. You can't really do both at the same time anyway, the heads NEED to be on and seated before the LIM goes on. The LIM's job (along with the RTV) is to fill the valley between the two heads.

I put RTV on the flat spot of the valley and around both sides of the coolant passages just for good measure. I also used the 2-piece metal & silicone gaskets. Followed the instructions and it's been bone dry since.

Here's a better writeup on the LIM and surrounding areas, it's what I followed and seems dead on:
https://dl.dropboxusercontent.com/u/464376/vehicles/1991 Explorer/40LIntakeGasketReplacement.pdf
 












In the write up posted, it is mentioned he left the fuel rail. It might be ok to leave the fuel injectors if you just cleaned them/ replaced o rings. You will still need to remove at least one fuel line, if not both to get room. One thing you should know, is pull the thermostat to get the coolant out first. I didn't and dumped about a cup of coolant in the oil on accident when I pulled the intake manifold. My oil never turned milky, and I ran it 5000 miles like that with no problems, however.
 






i actually removed the tstat hoping i could drive it but the external leak turned out to be worst than i originally suspected, i thought it was the heater core hose or tstat housing but upon closer inspection found it was coming from the engine, and where i remember the LIM mated with the block.


should i suspect the heads yet? im thinking aobut pulling the spark plugs particularly 1, 3 and 6 to see if they are wet so far the only condensation i have is under the oil cap it is very subltle, but oil level is good at normal, no milky, also no smoke out the exhuast but then again i stopped driving the car immediately when i noticed issues. should i find a wet cylinder should i get into the heads or just change the oil?

EDIT about torquing the heads and LIM, only my haynes manual advocates this but only when the heads are being installed i assume the heads are ok and it seems like i might be able to get away with just torquing the LIM WO touching the heads
 






x2 again on what 2stroke said. I'd get the fuel rail outta the way, disconnect both lines. Good opportunity to replace the o-rings too.

The head gasket could be bad and never leak coolant into the combustion chamber/oil. Really, the only way to know is to start digging. Hope that it's the LIM. If it's the heads, doing the job properly will be more than just changing gaskets.
 






pulled te LIM and found milky ness under the LIM also the the driver side valve cover was the milkyest but also the passenger side had some milk, whether its the LIM or heads the leaks seem near the front #1 cylinder by the heater hose base of the valley and rear by cylinder 3 and 6 ill post pix in a bit
 






A head gasket couldn't leak coolant UP into the valve cover area. It's likely the LIM that broke internally as well.
 






some pix as promissed

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SAM_0987_zpssads1blh.jpg
 






Looks like it's been wet in the front for a little while. Hard to tell exactly. Maybe peel the gasket off and start looking for cracks/compromised spots to find the smoking gun.

When I did my LIM, I could see a split in the ring that goes around the water port.
 






will do, i peeled off the gasket and the mating surfaces look good but havent looked at internals yet. i did notice alot of damage to the heater hose connection on the inside of LIM and alot of build up on the outside of the connection. ill post an update later.
 






after a week of inclement weather and school and then this morning cleaning the very dirty LIM i have yet to find a crack in the LIM however the gasket looked like it was going near the rear of the block im about to reinstall the new gasket. it had a bubble near the intake port on cylinder 6
 












You'd need to do a compression test to check the head gaskets.

There's two torque patterns for the LIM gasket. If the heads are off, then you alternate between head bolts and LIM bolts. It's in every Ford manual.
If the heads didn't come off, then they are already properly aligned for the LIM. And you only need torque the LIM.

Ford is going to give you same crappy gasket that was OE. In 1997, the LIM gasket was updated to its best design. So pick up a Ford or Felpro LIM gasket for a 1997 OHV engine.

http://www.explorerforum.com/forums/showthread.php?t=427909
 






right i used the torque and sequenced the tighning on the LIM but after idling for 10 minutes i am having alot of condensation coming out of the tail pipe. ill check the car when its cool to see if i have any coolant loss or maybe its running rich? im also thinking maybe the RTV bead just failed on me.
 






just opened the rad and found oil floating at the top. also some coolant is missing
 



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Condensation is normal, you'll get a lot. Believe it or not, for every gallon of gas you burn there's a gallon of water that comes out of the tail pipe in vapor. Condensation on a cool day means your catalytic converter hasn't heated up enough.

Oil in the coolant is troubling though. How's your transmission fluid? Coolant runs a higher pressure than oil (the oil isn't pressurized near the water jackets/passages) so regular motor oil can't really get in.
 






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